which powder for best case fill for 50 BMG

[big5ifty]

I've tried several powders in my 50 BMG, and of the ones I have access to, none of them gives me a good case fill.

I've tried US869, Vihtavuori 20N and 24N.

I like to have as little air in the case as possible, but with all of the above, I've had to use up to 3 grains of dacron filler to keep the powder against the primer.

It seems like this cartridge was designed for a powder that either is not commercially available, or is no longer manufactured.

So two questions :

1. what powder was the BMG cartridge originally made to be used with ?
2. what powder can give better case fill than US869, VV 20N or 24N ?

 

[SeabeeKen]

The powders you named were all made for the 50 as I recall. Others would be
Reloder 50, AR2218 ADI, H-50 BMG
Thats all I can think of at the moment

 

[Hoser]

There is no need for a filler.

I only use 20N29 and H50BMG, so I cant help with any other powders.

 

[coldboreshot]

What is the importance of your search for case "fill"? Are your concerns reliabilty, accuracy, or... ?

 

[big5ifty]

What is the importance of your search for case "fill"? Are your concerns reliabilty, accuracy, or... ?

This is a bolt action target rifle.

I'm still learning to shoot the rifle, so the truth is I can't shoot the difference yet, but I know from my other target rifles that achieving maximum powder burn in the barrel gives consistent accuracy.

Even though I can't shoot the difference yet, I know max powder burn is where it should be.

I always fill the air with dacron, it makes me feel better.

When I look at 236 grains of 24N41 in a TZZ case, the powder level is looks low

I use 750 grain monolithics which seat to the bottom of the neck / shoulder junction, and before the dacron it just seems there's a lot of air in there.

236 grains for US869 has slightly lower velocity, but equal case fill.

242 grains of 20N29 doesn't look better.

We do get Reloder 50 here, it's out of stock everywhere, I will keep an eye out for some.

Even if I use Lapua brass which has 13 grains less water capacity, the powder level fails to rise to where I'm comfortable not using the dacron.

First prize is not to use the filler, but then I want to see the powder level come up to where the air level in the case is small enough to ignore.

I've seated the bullets deeper and dropped the charge to come back to the same velocity, so that may be one option I need to test further, it just seems a waste of freebore.

My google-fu is weak, I can't get to what powder the cartridge was designed to use when they created it.

 

[coldboreshot]

This is a bolt action target rifle.

I'm still learning to shoot the rifle, so the truth is I can't shoot the difference yet, but I know from my other target rifles that achieving maximum powder burn in the barrel gives consistent accuracy.

Even though I can't shoot the difference yet, I know max powder burn is where it should be.

I always fill the air with dacron, it makes me feel better.

When I look at 236 grains of 24N41 in a TZZ case, the powder level is looks low

I use 750 grain monolithics which seat to the bottom of the neck / shoulder junction, and before the dacron it just seems there's a lot of air in there.

236 grains for US869 has slightly lower velocity, but equal case fill.

242 grains of 20N29 doesn't look better.

We do get Reloder 50 here, it's out of stock everywhere, I will keep an eye out for some.

Even if I use Lapua brass which has 13 grains less water capacity, the powder level fails to rise to where I'm comfortable not using the dacron.

First prize is not to use the filler, but then I want to see the powder level come up to where the air level in the case is small enough to ignore.

I've seated the bullets deeper and dropped the charge to come back to the same velocity, so that may be one option I need to test further, it just seems a waste of freebore.

My google-fu is weak, I can't get to what powder the cartridge was designed to use when they created it.

I have never had issues with accuracy variation related to case volume. In my loads, I have unfilled volume as well. I tend to wonder though, if the dacron itself is slightly suppressing the powder burn. I use Lapua and RWS brass, CCI, RWS and TulAmmo rusian primers with 750 Amax, Barnes Tac 750 and Lehigh Defense match projectiles and N20n29 powder exclusively. Never concerned myself with case volume. I even seat long because I shoot an Armalite AR50A1 factory platform with generous amount of freebore with staggering accuracy.

 

[RegionRat]

I can't get to what powder the cartridge was designed to use when they created it.

TLDR: It makes for interesting history, but it won't help you cause the MIL Spec folks didn't run commercially available cannister powders.

That is because it was considered a machine gun round and the batches were big enough to have bulk powders and loadings adjusted to their ammo specs. These bulk powders were not commercial cannister grade powders.

There were several projectiles and several powders used from inception just to the Viet Nam era, and then more from then on. Because many of those WW2 era applications were for higher and higher altitude bombers and long-range fighter escort, the low ends of the temp requirements were really cold before the war ended.

It was much later on that the design was considered important for single shot applications where repeatable single shot accuracy was desired.

Many of the first Korean and Viet Nam war sniping applications used common ammo, but later on there were efforts to load for sniping by just upgrading the original materials with more careful preparations of those original bulk materials.

At some point after the Canadian Snipers came and saved our butts, there was more GOV support for paying attention to improving the ammo for sniping. By that time, the hobby folks were already doing the same work using commercially available powders and surplus pull-down powders with custom bullets.

So if you follow the later ELR crowd rather than the "original" designs, you will be better off.

 

[rmr]

Its been a while since I've shot competitively with the 50, but i have loaded a lot of shells over the years.

I would not be concerned with Case fill. My favorite powder was 20N29, because it was the best performing powder with the 810gn BR solids that I favor. (N41 was too fast, and I got better results with N29 vs H50BMG. R50 wasn't available at the time) As with just about any other cartridge, your main goal from a powder perspective is the correct burn rate (velocity vs pressure) and whatever provides the lowest SD's

when working up loads, I tried to start at 2650 to 2750 fps window, looking for the lowest SD's. I would follow up with a long distance ladder test / accuracy at 600yds. later on, i combined all of the above in one long range session, mainly for economics. 8lb kegs of powder are not cheap. I don't know if its still true or not, but N29 was historically quite variable in burn rate from lot to lot. you had to test every lot for velocity, so you learned to buy a lot of it when you did. I don't ever remember even looking at what the case fill was. at the end of the day, all i really cared about was small Aggs.

I would be concerned with the Dacron however. I have no idea if its actually an issue or not, but I would worry about it getting hung up in the muzzle brake. I once had a clamshell brake fail on me in the middle of a match some 20y ago. I don't want to ever experience that again.